Ligation of the hypoglossal nerve at 7 days post partum results in irreversible chromatolysis and subsequent cell death of neurons of hypoglossal nucleus. In contrast, ligation of the hypoglossal nerve in 3 week old animal is accompanied by reversible chromatolysis with functional recovery of the affected neurons within 45-55 days following the axonal injury. The use of these two maturity states therefore will provide a model for further investigations of the basic sequence of how the cell body changes following injury to axon relate to the processes of nerve regeneration and degeneration.